Pterodaustro: a Filter-Feeding Pterosaur

Pterodaustro guinazui was an Early Cretaceous pterosaur from central Argentina with a feeding apparatus unlike that of most vertebrates. Its upturned lower jaw carried hundreds of very long, fine teeth that formed a dense comb; the upper teeth were short and rounded. Hundreds of individuals, eggs, embryos and young animals make the genus unusually informative about growth, but its pink colour and exact feeding posture remain unproven.

Quick facts

From a single bone to an exceptional sample

José Bonaparte named Pterodaustro in 1970 from a femur found in the Lagarcito Formation. Later work at Loma del Pterodaustro in San Luis Province produced hundreds of specimens, including skulls, articulated skeletons and material from different growth stages. The type specimen, PVL 2571, is an isolated femur; the broader sample, rather than the type alone, explains why so much is known about the genus.

The deposits formed beside a broad, shallow lake. Fine sediment preserved small bones and fragile teeth. The abundance of individuals indicates repeated use of the locality, but does not by itself prove a single mass death, a permanent breeding colony or complex social behaviour.

A lower jaw built to strain small food

The lower jaw curved upward and carried hundreds of slender teeth, each only a fraction of a millimetre thick and reaching several centimetres in length. They were densely spaced and could flex. The short upper teeth contrasted with this comb. Microscopic anatomy identifies the long elements as true teeth with dental tissues, not a keratin bristle fringe.

When water and food passed through the lower tooth row, small particles could be retained. The anatomy strongly supports a filter-feeding role, probably involving tiny aquatic organisms such as crustaceans. But the fossils cannot show whether the animal moved its head sideways, swept forward or used another motion. Nor do they preserve a complete inventory of its meals.

Two nearly complete skeletons preserve sand and small pebbles in the body region. Researchers have interpreted these stones as gastroliths that may have helped process hard food. The stones are directly present; their digestive function is inferred, and the small sample does not prove that every individual carried them.

Growth recorded in bone

Histological study of bones from different-sized individuals suggests rapid growth during roughly the first two years, when juveniles reached about half the adult linear size. Growth then slowed but continued for several more years. The largest known adults had wingspans near 2.5 metres; the smallest young specimens were around 30 centimetres across the wings, not a separate dwarf species.

Outer bone layers preserve a slowdown or cessation of growth, supporting determinate growth rather than indefinite increase. These estimates depend on reading growth marks and assigning isolated bones to age classes. They are stronger than guesses based only on an illustration, but are not direct observations of a living animal’s annual schedule.

A large femur has been described as containing tissue comparable to medullary bone in birds, which can provide calcium for eggshell production. It may indicate a reproductive female, but the identification remains cautious because other endosteal or pathological tissues can look similar. One bone cannot establish the sex ratio or breeding behaviour of the population.

Eggs, embryos and early life

An embryo preserved inside an egg links that egg to Pterodaustro. Another three-dimensional egg preserves shell structure and a clearer volume than many flattened pterosaur eggs. The surrounding sediments indicate a lake environment, but comparisons with modern waterbirds do not prove that Pterodaustro built the same kind of nest.

Young individuals had wing proportions consistent with flight, yet the timing of their first flight is debated. A skeleton can show that the wing was developing; it cannot record whether a hatchling left the ground immediately or remained near adults. The many growth stages make this question testable, but they do not settle every aspect of parental care.

Was Pterodaustro pink?

Popular reconstructions often give Pterodaustro a pink colour by analogy with flamingos, which obtain carotenoid pigments from food. No reliable fossil pigment signal establishes that colour in Pterodaustro, and its metabolism of such pigments is unknown. Similar feeding mechanics do not guarantee identical colour, skin or social behaviour. Pink is an artistic possibility, not a demonstrated fact.

The fossils provide unusually strong evidence for the tooth comb, a rich growth series, eggs and embryos. They support filtering small aquatic food and a life associated with lake deposits. Exact feeding movements, a universal gastrolith habit, parental care and colour remain less certain. Those distinctions make Pterodaustro one of the most informative profiles in the pterosaur catalogue, not a licence to treat every reconstruction as directly preserved.